User Guide
Add the audio file
MP3, WAV, M4A, AAC, OGG, Opus, WMA, FLAC and AIFF are all accepted, and video files work too if you want their soundtrack. Up to 300 MB.
Check whether your source is lossless
FLAC, WAV and AIFF are lossless. Converting them to MP3, AAC or OGG is a one-way door — keep the original if you may need it again.
Choose the output format
MP3 for universal playback, WAV for editing software, AAC for Apple devices and efficiency, OGG for open, patent-free output.
Convert
The file is decoded and re-encoded at the target codec’s standard settings. Audio-only conversion is quick, typically well under a minute.
Download and confirm it opens
Particularly worth doing when converting for a specific device — a car stereo, an older player, a piece of studio software.
For part of a file only
Use the Audio Cutter to set a start and end point rather than converting the whole thing and trimming afterwards.
About the Audio Converter
This tool converts audio between MP3, WAV, AAC and OGG, and reads a considerably wider range of inputs than that — including the awkward formats that tend to be the reason someone needs a converter in the first place. It runs entirely in your browser.
The formats it will read
| Input | What it usually is | Common problem it causes |
|---|---|---|
| WMA | Windows Media Audio | Will not play on Apple devices or most phones |
| M4A | AAC in an MP4 container | Rejected by software expecting .mp3 |
| FLAC | Lossless compression | Large; unsupported by many car stereos |
| AIFF | Apple uncompressed | Very large; a Mac-centric format |
| Opus | Modern low-latency codec | Excellent quality, patchy device support |
| OGG | Vorbis audio | Not supported by much consumer hardware |
Opus, defined in RFC 6716 (Opus), is worth singling out: it is technically the strongest of these at low bitrates and is what most voice and messaging apps now use, which is why voice notes so often arrive in a format nothing on a desktop will open.
Lossless and lossy — the distinction that matters
Lossless formats keep every sample. WAV and AIFF store them uncompressed; FLAC compresses them the way a ZIP file does, typically to 50–60% of the original with the data perfectly recoverable (see the Xiph FLAC format overview). Decompress a FLAC and you get the original back, bit for bit.
Lossy formats — MP3, AAC, OGG, Opus — permanently discard audio judged inaudible, which is how they reach a tenth of the size.
The rule that follows is simple and worth taking seriously: lossless to lossy is irreversible. Converting FLAC to MP3 is fine and often exactly right for a phone or a car stereo, but keep the FLAC. Converting the MP3 back to FLAC later produces a large file containing the MP3’s quality — the discarded detail is gone for good.
Choosing the output
MP3 when compatibility is the point. It is not the most efficient codec, but it is the only one that plays on absolutely everything.
WAV when software downstream needs uncompressed input. Audio editors, some transcription engines and most mastering tools do. Expect about 10.1 MB per minute at CD quality — a full album runs to roughly 450 MB.
AAC for Apple devices, or when you want better quality per megabyte than MP3. It is the default audio format inside MP4 and the native choice across iOS and macOS.
OGG for open, patent-free output, particularly for game engines and Linux software.
Two practical cautions. Converting a lossy file to WAV does not restore anything — it produces a big file holding exactly the quality that was already there. And converting between two lossy formats always costs a generation, so go back to the best source you have rather than chaining conversions.
Privacy and limits
Everything runs through a WebAssembly build of FFmpeg loaded into the browser tab on first use (about 30 MB, cached afterwards). Nothing is transmitted — there is no upload and no copy of your file on any server. A single-threaded WebAssembly module addresses only about 2 GB of memory, so files over 300 MB are rejected and anything above 60 MB warns that it will be slow. Audio files are small compared with video, so most conversions finish in well under a minute.
Frequently Asked Questions
Which input formats are supported?
MP3, WAV, M4A, AAC, OGG, Opus, WMA, FLAC and AIFF, plus video files if you want their soundtrack. FFmpeg reads the actual stream rather than trusting the extension, so unusual files are generally handled.
What is the difference between lossless and lossy?
Lossless formats — WAV, AIFF and FLAC — keep every original sample. Lossy formats such as MP3, AAC, OGG and Opus permanently discard audio judged inaudible, which is how they reach roughly a tenth of the size.
Can I convert MP3 back to FLAC to improve it?
No. The detail an MP3 encoder discarded is gone permanently. Converting to FLAC afterwards gives you a large file containing exactly the MP3’s quality and nothing more. Always go back to the original lossless source.
How do I get a WMA file onto my iPhone?
Convert it to MP3 or AAC. WMA is a Microsoft format that Apple devices have never supported; AAC is the native iOS choice and MP3 works universally.
Why will my voice note not open on my computer?
It is probably Opus, which most messaging apps now use because it performs well at very low bitrates. Desktop support is patchy. Converting to MP3 makes it open anywhere.
How big will a WAV file be?
About 10.1 MB per minute at CD quality — 44.1 kHz, 16-bit, stereo works out to 1,411 kbps. A full album comes to roughly 450 MB. Only choose WAV when software actually requires uncompressed audio.
Should I convert FLAC to MP3 for my car?
Yes, if the car will not read FLAC — many will not. Just keep the FLAC files. The MP3s are a convenience copy, not a replacement, because the conversion cannot be undone.
Does my audio file get uploaded?
No. The conversion runs inside your browser through a WebAssembly build of FFmpeg. The file is read from your disk into the tab’s memory and written straight back out.